Plantar pressure during running in subjects with chronic ankle instability.

BACKGROUND: It has been suggested that dynamic foot and ankle mechanics predispose individuals with CAI to repetitive episodes of the ankle ``giving way.'' Plantar pressure variations during a walking gait have been detected in those with CAI, but more dynamic conditions for analysis are needed. The purpose of this study was to evaluate plantar pressure distributions during a running gait in individuals with CAI, individuals who suffered a lateral ankle sprain, but did not develop CAI (AS), and subjects with no history of a lateral ankle sprain (CON). MATERIALS AND METHODS: Forty-five subjects [15 in each group, healthy males (18) and females (27), age 18 to 45] were recruited from University communities to participate in this study. Plantar pressure distributions were analyzed on a Tekscan© plantar pressure mat at 66 frames per second during a running gait at a controlled speed. The following variables were obtained: rearfoot medial/lateral (M/L) pressure ratio at foot strike (FS) and center-of-pressure (COP) trajectory during the initial loading response (heel strike to initial peak GRF). Separate one-way ANOVA with Tukey's post-hoc were used to test for group differences. The significance level was defined as p < 0.05. RESULTS: The CAI group had a significantly more lateral ratio (0.97 ± 0.12) at FS when compared to the CON (1.01 ± 0.13) and AS (1.11 ± 0.13) groups. The CAI subjects had a lateral COP trajectory during the loading phase (7.97 degrees ± 11.02), while both the AS (-3.68 degrees ± 10.24) and CON groups (-6.27 degrees ± 9.86) had medial trajectories. The difference was significant between the CAI group and both the AS and CON groups (all significant {\it p} values were less than 0.05). CONCLUSION: Our results confirm that CAI subjects have a more lateral foot positioning and loading pattern during a barefoot running gait when compared to both the CON and LAS groups. CLINICAL RELEVANCE: Clinicians treating patients with CAI should consider providing interventions to decrease the amount of rearfoot inversion at FS and during loading in order to create a more medial COP trajectory upon impact.